38 CFR § 3.654 - Active service pay.
(a) General. Pension, compensation, or retirement pay will be discontinued under the circumstances stated in § 3.700(a)(1) for any period for which the veteran received active service pay. For the purposes of this section, active service pay means pay received for active duty, active duty for training or inactive duty training.
(b) Active duty or active duty for training.
(1) Where the veteran receives active service pay as a result of returning to active duty status or active duty for training as described in § 3.6(c), with the exception of annual active duty for training typically performed 15 days each year by reservists and members of the National Guard and Active Duty for Special Work to receive training (see paragraph (c) of this section), the award will be discontinued effective the day preceding reentrance into active duty or active duty for training status. If the exact date is not known, payments will be discontinued effective date of last payment, and the effective date of discontinuance will be adjusted to the day preceding reentrance when the date of reentrance has been ascertained from the service department.
(2) Payments, if otherwise in order, will be resumed effective the day following release from active duty or active duty for training if notice from the Department of Defense of such release or a claim for recommencement of payments is received within one year from the date of such release; otherwise, payments will be resumed effective one year prior to the date of receipt of a new claim. Prior determinations of service connection will not be disturbed except as provided in § 3.105. Compensation will be resumed based on the combined evaluation in effect at the time payments were discontinued. If a reduction in evaluation that lowers the combined evaluation is considered warranted, the provisions of § 3.105(e) will apply. If a disability is incurred or aggravated, or a service-connected disability worsens in the most recent period of service, compensation for that disability or increase in disability cannot be paid unless a claim therefor is filed.
(c) Training duty. Prospective adjustment of awards may be made where the veteran waives his or her Department of Veterans Affairs benefit covering anticipated receipt of active service pay because of expected periods of active duty for training (annual active duty for training typically performed 15 days each year by reservists and members of the National Guard or Active Duty for Special Work to receive training) or inactive duty training. Where readjustment is in order because service pay was not received for expected training duty, retroactive payments may be authorized if a claim for readjustment is received within one year after the end of the fiscal year for which payments were waived.